Filling system for hermetically sealed batteries

ABSTRACT

Electrochemical cell containers having an improved seal arrangement including a polymeric member carrying a metal pin in a bore extending therethrough.

BACKGROUND OF PRIOR ART

This invention relates to electrochemical cells of improvedconstruction. Specifically it is concerned with cells having an improvedseal in the filler opening of the cell container for the introduction ofa fluid cell component or components into the container.

With the advent of high energy density nonaqueous cells generallyutilizing fluid components such as thionyl chloride and sulfur dioxidedepolarizers and various reactive organic electrolyte solvents, thedesign and sealing of the filler opening of such cells has becomeincreasingly important. For purposes of this invention, the term "fluid"is meant to describe any component capable of flowing into the cellcontainer. In most instances, the component will be a liquid, includingsolutions.

Electrochemical cells such as rechargeable lithium cells having a liquidelectrolyte and incorporating various components may make use of theinvention. For example, see U.S. Pat. No. 4,118,550 and U.S. Pat. No.3,998,658 for cells of this type. The following listed U.S. Patents showvarious lithium-halogen batteries or cells of another type making use ofcell containers in which a fluid component is introduced into thecontainer though a filler opening: U.S. Pat. Nos. 4,105,833; 4,135,519;4,132,836; 4,166,887; 4,211,832 and 4,360,573. These cells may also makeuse of this invention. All of these patents are incorporated herein byreference.

It should be understood that, if a fluid component is used in accordancewith this invention, it need be in fluid form only at the time of itsintroduction into the cell container. Thereafter, it may solidify orassume any other form as required by the particular cell involved.

BRIEF SUMMARY OF THE INVENTION

This invention provides an improvement in electrochemical cellconstruction wherein the cell container filler opening includes a uniquearrangement for filling and sealing the cell.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top elevational view of an electrochemical cell illustratingthe improved construction of the invention.

FIG. 2 is a side elevational view in section along line 2--2 of FIG. 1with parts of the cell removed to show the invention in more detail.

FIG. 3 is a schematic arrangement for effecting the filling of a cellconstructed according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to FIGS. 1 and 2, a hermetically sealed cell isillustrated showing the preferred form of the fill/seal arrangement ofthe invention. The cell comprises a container 10 of metal such asstainless steel. Container 10 has an open top or end which is closed bymeans of a lid 12, also of stainless steel. Lid 12 is welded tocontainer 10. The cell also includes anode means, in this casecomprising a lithium element 14 and an embedded anode current collectorelement 18. Current collector 18 is a relatively thin element of metalsuch as stainless steel, nickel or zirconium. A conductor leadfeedthrough assembly 20 including lead 22 of stainless steel or othersuitable metal is spot welded to collector element 18. Electrical lead22 is of sufficient length to extend out of the container 10 for thepurpose of making an external electrical connection thereto. Conductor22 and the related feedthrough assembly 20 are sealed from the remainderof the cell contents internally by means including a protective sheathelement generally designated 24 which surrounds the feedthrough assemblyinternally. Sheath element 24 is of a material which, in addition tobeing a non-conductor of electricity is also non-reactive with thecontents of the cell. Materials found to perform satisfactorily for thispurpose are the fluoropolymers, such as the one available under theTradename "Halar", a trademark of the Allied Chemical Company. Othernonreactive electrical insulating materials may be used for element 24as well.

The anode assembly comprising the lithium element 14, for example, andcurrent collector 18 is preferably fitted within a separator enclosure30 which separates the anode from the electrolyte and the cathode means.Separator 30 is preferably of polypropylene or polyethylene or othermicroporous polymeric material which allows ionic conductiontherethrough but prevents electron transport. A preferred arrangment forsuch a separator is shown in co-pending application Ser. No. 553,582,filed Nov. 21, 1983, incorporated herein by reference.

The anode assembly is positioned in container 10 as shown in FIG. 2 withall the anode surfaces spaced from the inner surface of the container soas to guard against contact between the anode and the container.Likewise, a pair of carbon or other suitable cathodes 32 may bepositioned to each side of the anode assembly and included in thecontainer so as to electrically contact the inside wall thereof.Preferred cathodes of the carbon type are described more fully, forexample, in U.S. Pat. No. 4,118,550 entitled Aprotic Solvent ElectrolyteBatteries, issued Dec. 21, 1976. These patents are incorporated hereinby reference.

In the particular embodiment illustrated, container 10 being ofelectrically conducting material serves as a cathode current collectorin direct contact with the cathodes 32 in container 10. Consequently, anelectrical lead 34 may be attached directly to container 10 for cathodiccontact and connection.

In accordance with the present invention a fill port seal arrangementplug construction is generally indicated at 40. Subassembly 40 includesa metal sleeve 42, of stainless steel or the like which includes apolymeric plug 44 having a passageway or bore extending therethrough.Plug 44 is preferably positioned at an inner location as shown in FIG.2. Plug 44 is made of a compressible body of a suitable non-reactivepolymeric material (to the system involved) such aspolytetrafluoroethylene (PTFE) or other suitable fluoropolymer.Typically, polypropylene, polyethylene and other such polymericmaterials which are non-reactive to the system may be used.

Sleeve 42 is welded into an opening in lid 12 as shown. Plug 44 may bemolded into sleeve 42 or it may be preformed and inserted into thesleeve as shown. In such an arrangement, the sleeve will include aninner annular shoulder 46 against which plug 44 rests. The bottom ofsleeve 44 is open as at 45 and is crimped or otherwise formed as shownat 48 so as to retain plug 44 therein. Any other means suitable forretaining the plug in the sleeve may be used.

As can be seen in the drawing, an upper opening 50 in sleeve 42 leads toa relatively small opening or bore 52 in plug 44 which in turn leads tothe interior of container 10. This opening may be formed in the plug orpredrilled or formed by any suitable means.

With such a plug in place as shown in the drawing, a hypodermic-likeneedle or other suitable conduit may be inserted through plug 44. Bymeans of such an arrangement, container 10 may be evacuated and thenfilled with any fluid component or components of the cell, such as theaforementioned fluid electrolyte material.

Following the filling of container 10 by means of penetration andremoval of the needle or the like from plug 44, a metal plug member 56is inserted into sleeve 42 by force-fit. Preferably, the top thereof iswelded into position as shown at 54.

Filling of the cell is preferably accomplished by using an arrangment ofthe type shown in FIG. 3. This arrangement includes a hollow needle 60which is shown schematically and which is inserted through the bore ofplug 44 in fill port 40 and into the interior of cell container 10.Evacuation and filling is accomplished through this needle. The exteriorend of needle 60 is connected to a 3-way valve 62.

In one position (shown), valve 62 interconnects needle 60 to vacuum line64 which is connected to a source of vacuum as indicated in the drawing.

In a second position (not shown), valve 62 interconnects needle 60 to afluid fill source means generally indicated at 66. Fill source means 66includes a reservoir 68 which contains an amount of a fluid of the typeto be included in cell 10. Quantities of the fluid may be passed to ameasuring container 70 through a valve 72 and conduit 74. A source ofinert gas may be provided as shown to provide a protective blanket overthe fluid in reservoir 68 and container 70.

Once evacuation of cell container 10 has been accomplished, a quantityof fluid, which has been passed to container 70 by means of an openedvalve 72 and conduit 74, can be allowed to flow into the cell containerby closing valve 72 and by placing valve 62 in its second positionthereby establishing flow connection between container 70 and cellcontainer 10 by means of conduit 76.

Upon completion of the filling of cell container 10 a prescribed levelor quantity, the needle is removed and the cell is then sealed asdescribed hereinabove.

While a preferred embodiment has been described in detail, this has notbeen done for purposes of limitation but for illustration. It is to beunderstood that various changes may be made in the form, constructionand arrangement of the several elements, parts and components describedand the various material used without departing from the spirit andscope of the invention. Hence, there is no intent to be limited to thedetails shown or described herein except as the same are included in theclaims or may be required by disclosures of the prior art.

What is claimed is:
 1. In an electrochemical cell of the type having acontainer for housing cell components, an opening in the container forintroducing fluid components into the container, and means closing thecontainer opening, the improvement comprising polymeric plug meanscarried in the opening for closing it, the plug means comprising apolymer body having a relatively small opening extending therethroughwhereby a fluid component may be introduced into the container byinsertion of a hypodermic-like needle into the plug means opening, and atapered metal plug inserted into the opening in the polymeric body forclosing it, and additional means securing the metal plug in the opening.2. The electrochemical cell of claim 1 wherein the polymer is PTFE. 3.The electrochemical cell of claim 1 wherein the plug means furthercomprises a sleeve for receiving the polymeric body and holding it inplace, the sleeve being positioned in the container opening and sealedto the container about the opening.
 4. The electrochemical cell of claim3 wherein the sleeve and container are of metal and are welded togetherabout the container opening, the sleeve including an internal shoulderagainst which the outer end of the polymeric body rests, the sleevebeing formed at its inner end for holding the polymeric body in positionand wherein the outer end of the metal plug is welded to the metalsleeve.
 5. The electrochemical cell of claim 4 wherein the sleeve andmetal plug are of stainless steel and the polymeric is PTFE.